The present application relates generally to an improved data processing apparatus and method and more specifically to mechanisms for reusing snapshots in a network data management protocol (NDMP) backup operation.
NDMP is an open standard protocol for network-based backup for network-attached storage. The protocol allows backup and network-attached file server vendors to focus investment on functionality instead of excessive porting, and gives users an unprecedented level of choice and interoperability. The purpose of the NDMP protocol is to allow a network based data management application, such as a data backup application, to control the backup and retrieval of data in an NDMP-compliant storage environment without installing third-party software on the storage devices themselves.
In NDMP the control and data transfer components of the data management operation are separated. This separation allows for complete interoperability at a network level. The storage system vendors need only be concerned with maintaining compatibility with one, well-defined protocol. The data management vendors can place their primary focus on the sophisticated central data management administration software.
The NDMP protocol is targeted towards the process of data management: backup, restore, replication, mirroring, etc. The protocol is specifically intended to support tape drives. However, the protocol can be used for other applications and support other media as well. More information about NDMP, including the standard specifications, may be found at the NDMP official website www.ndmp.org
The most recent version of NDMP, i.e. NDMP v5, provides support for snapshots. A snapshot is a mechanism for quickly creating and labeling a consistent copy of a volume or a file system. In other words, the snapshot represents the state of the volume or file system at a particular instance in time. Many separately labeled snapshots can co-exist on a storage device at a same time and can be used as input to a backup or data replication operation. In NDMP v5, support for snapshots, which are used by many vendors of database systems, is provided such that the data management application (DMA) engine can issue commands to have a data service create and label snapshots so that they can be later used as the source for a data management operation, such as a backup operation or data replication operation.
Currently, with NDMP, snapshots are taken with regard to every directory of a file system or volume. In large file systems, such as file systems with millions of small files, the overhead to take a snapshot or delete a snapshot can reduce the overall bandwidth of the backup and increase the time it takes to backup a file system.